1. Field of the Invention
The invention relates to a silicon-based microphone structure with an electromagnetic interference shielding means, low cost, and minimized package size.
2. Description of the Related Art
Many electronic devices have microphones inside. Providing a microphone to have an electromagnetic interference shielding means, low cost, and minimized package size is required.
U.S. Pat. No. 6,781,231 discloses a microelectromechanical system package with an environmental and interference shield. As shown in FIG. 1, a cover 20 is disposed on a substrate 23. The cover 20 serving as an environmental and interference shield includes an outer cup 25a and an inner cup 25b. A plurality of electronic elements 12 is disposed in a chamber 36 formed by the cover 20 and the substrate 23. The cover 20 has a plurality of acoustic ports 44 and 48 allowing the electronic elements 12 to receive external sound.
In operation, however, acoustic resonance is generated in the chamber 36 so that the operating frequency band of the electronic element 12 is narrow. Also, the size of the microelectromechanical system package can not meet modern electronic device requirements for extreme compactness.
U.S. Patent Application Publication No. 2007/0278601 discloses a MEMS (micro-electro-mechanical system) device. As shown in FIG. 2, a MEMS die 110 is mounted on a chip carrier 120 and encapsulated by an enclosure 130. The chip carrier 120 has an acoustic hole 125 covered by the MEMS die 110. The enclosure 130 is used for preventing transmission of any electromagnetic radiation from the MEMS die 110, and any electromagnetic radiation from interfering with the MEMS die 110. The enclosure 130 may be molded using a thermoplastic or thermosetting polymer material, such as epoxy molding compound, liquid crystal polymer, or polyetheretherketone (PEEK), and an electrically conductive material, such as metal particles or carbon fibers or fillers.
Similarly, in operation, acoustic resonance is generated in the enclosure 130 so that the operating frequency band of the MEMS die 110 is narrow. Also, the size of the MEMS device 110 can not meet modern electronic device requirements for extreme compactness.
U.S. Pat. No. 6,522,762 discloses a silicon-based sensor system. As shown in FIG. 3, a transducer 1 and an integrated circuit chip 3 are flip-chip mounted on a silicon carrier substrate 2. The transducer 1 and the integrated circuit chip 3 are electrically connected. The second surface of the silicon carrier substrate 2 is supplied with a plurality of solder bumps 22 for surface mounting onto a printed circuit board (not shown). A lid 5 provides EMI (electromagnetic interference) shielding. An EMI shield 16 is a conductive polymer layer such as silver epoxy, or a metal layer such as electroplated or evaporated Cu or Au.
The lid 5 and the EMI shield 16 are formed not in advance but during the assembly of the silicon-based sensor system. Therefore, the productions of the silicon-based sensor systems are not easy and convenient.
U.S. Pat. No. 7,202,552 discloses a MEMS package using flexible substrates. As shown in FIG. 4, the MEMS package 70 has a MEMS device 40 attached to the flexible substrate 10. A metal cap 54 encapsulates the MEMS device 40 on the flexible substrate 10. The flexible substrate 10 is folded over the metal cap 54 and glued to the top of the metal cap 54. The metal cap 54 and the metal layer of the flexible substrate 10 are electrically connected to form a Faraday cage for EMI/RF shielding.
Similarly, the size of the MEMS package can not meet modern electronic device requirements for extreme compactness. Furthermore, packaging of the MEMS device is complicated, and the flexible substrate 10 is not protected from EMI and RF by any shielding means.